System and method for improving efficiency of wirelessly transmitting video packets

ABSTRACT

A device, system and method are provided for wirelessly transmitting a sequence of video packets containing video data for one or more video frames. An importance metric associated with a priority of transmitting each individual packet in the sequence of video packets is independently computed, a retry limit or packet lifetime for each individual video packet in the sequence of video packets is independently determined based on the importance metric, and each video packet in the sequence of video packets is attempted to be transmitted. If the transmission attempt for an individual video packet in the sequence fails, the transmission attempt is repeated for up to the retry limit or the packet lifetime independently determined for the individual packet or until a successful transmission is achieved, whichever occurs first.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Indian Patent Application No.201841007160, filed Feb. 26, 2018, which is hereby incorporated byreference in its entirety.

FIELD OF THE INVENTION

Embodiments of the invention relate to the field of transmitting videodata over wireless networks. Some embodiments of the invention relate tomethods that can be implemented in a medium access control (“MAC”) layerof a wireless local area network (“WLAN”).

BACKGROUND OF THE INVENTION

Video applications, such as video streaming and interactive videoapplications, are very sensitive to packet loss and delay. Video data iscommonly transmitted over wireless networks, e.g., using layer 2technology, such as wireless local area networks (“WLAN”), due toadvantages of wireless networks, such as ease and cost of deployment andmaintenance. However, wireless networks are typically lossy networksthat often drop video packets and degrade video playback performance.

Accordingly, there is a need in the art to improve the transmission ofvideo data over wireless networks.

SUMMARY OF THE INVENTION

According to some embodiments of the present invention, there isprovided a method and device for improving the transmission of videodata over wireless networks. In an embodiment, a sequence of videopackets is wirelessly transmitted containing video data for one or morevideo frames. An importance metric associated with a priority oftransmitting each individual packet in the sequence of video packets maybe independently computed, a retry limit or packet lifetime for eachindividual video packet in the sequence of video packets may beindependently determined based on the importance metric, and each videopacket in the sequence of video packets may be attempted to betransmitted. If the transmission attempt for an individual video packetin the sequence fails, the transmission attempt may be repeated for upto the retry limit or the packet lifetime independently determined forthe individual packet or until a successful transmission is achieved,whichever occurs first.

The retry limit or packet lifetime of the video packets may bedynamically adjusted in real-time. The retry limit or packet lifetime ofthe video packets may be independently determined to be directlyproportional to the importance metric of each video packet.

The importance metric of the video packet may be computed based on oneor more factors selected from the group consisting of: a video frametype, an order of a frame fragment, and a success or failure streak ofthe sequence of video packets. The importance metric of the video packetmay be computed based on the video frame type of the video packet, and avideo packet associated with an I video frame has a higher importancemetric than a video packet associated with a P frame, which in turn hasa higher importance metric than a video packet associated with a Bframes.

The importance metric of the video packet may be computed based on theorder of the frame fragment, such that a packet associated with asubsequent (Nth) frame fragment is assigned a relatively greaterimportance metric than a prior (N−1th) frame fragment. A separate valueof the order of the frame fragment for each different video frame typemay be maintained.

The importance metric of the video packet may be proportional to astreak value counting the number of successful transmissions of a groupof the video packets associated with each I frame. The streak value maybe incremented each time one of the group of video packets issuccessfully transmitted, or decremented each time one of the group ofvideo packets is not successfully transmitted.

A separate streak value for each different video frame type may bemaintained. An I frame streak counter may be initialized at the start ofa new streaming session and incremented upon each successful I framevideo packet transmission. A P frame streak counter may be initializedfor each new group of frames associated with a new I frame andincremented upon each successful P frame video packet transmission. A Bframe streak counter may be initialized for each new group of framesassociated with a new I frame and incremented upon each successful Bframe video packet transmission.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features, and advantages of the presentinvention, as well as the invention itself, is more fully understoodfrom the following description of various embodiments, when readtogether with the accompanying drawings.

FIG. 1A schematically illustrates a system for wirelessly transmitting asequence of video packets over a wireless local area network (“WLAN”),in an Access Point (“AP”) mode, according to an embodiment of theinvention.

FIG. 1B schematically illustrates a system for wirelessly transmitting asequence of video packets over a wireless local area network (“WLAN”),in a Station (“STA”) mode, according to an embodiment of the invention.

FIG. 2 schematically illustrates a video streaming system, according toan embodiment of the invention.

FIG. 3 schematically illustrates a WLAN MAC subsystem, according to anembodiment of the invention.

FIG. 4 illustrates an exemplary frame type breakdown of two groups ofpictures (“GOP”), according to an embodiment of the invention.

FIG. 5 is a flowchart of a method for wirelessly transmitting a sequenceof video packets containing video data for one or more video frames,according to an embodiment of the invention.

FIG. 6 is a flowchart of a method for selecting a parameter table usingtransmission rate, according to an embodiment of the invention.

FIG. 7 is a flowchart of a method for selecting a parameter table usingqueue backlog, according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the present invention improve the performance of videoapplications implemented over lossy networks, by reconfiguring a commonmedium access control (“MAC”) layer of a WLAN video streaming system toefficiently determine whether to drop one or more packets to reducecongestion while ensuring smooth video playback.

The 802.11 standard specifies a MAC layer, which provides a variety offunctions that support the operation of 802.11-based WLANs. In general,the MAC layer manages and maintains communications between 802.11stations (radio network cards and access points) by coordinating accessto a shared radio channel and utilizing protocols that enhancecommunications over a wireless medium. Often viewed as the “brains” ofthe network, the 802.11 MAC layer uses an 802.11 Physical (PHY) Layer,such as 802.11b or 802.11a, to perform the tasks of carrier sensing,transmission, and receiving of 802.11 frames.

The MAC layer is a sub-layer of the layer 2, and the layer 2 refers to adata link layer concerned with moving data across physical links in thenetwork. The MAC layer handles the transmissions, retransmissions anddropping of frames based on channel characteristics/parameters, such asa maximum number of transmission (or retransmission) attempts allowedfor a packet (referred to as a “retry limit”) or a maximum amount oftime allowed for transmitting (or retransmitting) a packet (referred toas a “packet lifetime”). The MAC layer may also monitor the relativepriority/importance of individual video frames based on the amount ofinformation in each video frame, dependency between the video frames,and differences with respect to preceding frames. The importanceinformation generated by the MAC layer may be utilized in combinationwith the above channel characteristics/parameters to determine therelative importance of the video packets.

For example, when a wireless device queues a packet for transmission,the device operates over the MAC layer to request a transmission channeland, upon successful channel acquisition, uses the wireless MAC totransmit the packet. If the packet transmission is successful, thedevice proceeds to process a next packet in the transmission queue.However, if the packet transmission fails, e.g., as inferred by amissing acknowledgment from the device intended to receive the packet,then the device retransmits the packet using the MAC layer until theretry limit is reached and/or the amount of time for attemptingretransmission has exceeded the packet lifetime, whichever occurs first.

In conventional methods and devices, retry limits and packet lifetimesare fixed. Conventional retry limits and packet lifetimes are staticallyconfigured for a system and are not updated/changed thereafter (e.g.,during operation or transmission). Instead, conventional methods use asingle retry limit/packet lifetime for all packets to be transmittedthat are of same category (e.g., video, voice, data, etc.). For example,conventional methods may utilize a single constant packet lifetime of500 ms for all packets. Because conventional systems use the same retrylimits and packet lifetimes, all frames have the same probability ofbeing dropped.

In contrast to conventional methods and systems of wireless transmissionof video data, embodiments of the present invention dynamically adjustretry limits and packet lifetimes in real-time for each individual videopacket proportionally to the packet's importance or priority (e.g.,compared to other packets to be transmitted). By using packet-specificretry limits and packet lifetimes proportional to packet importance,embodiments of the present invention have a relatively lower probabilityof dropping higher priority frames compared to lower priority frames. Byshifting more transmission resources to higher priority frames, suchembodiments increase the overall transmission success rate of higherpriority frames compared to conventional methods to improve the overallwireless video performance, allowing for smoother video playback. Inaddition, reducing the retry limits and packet lifetimes of lowerpriority frames may reduce wireless network congestion, and increase theoverall transmission speed.

In some embodiments of the present invention, the longest durationpacket lifetime utilized may be the same as (e.g., 500 ms) or shorterthan (e.g., 200 ms) conventional packet lifetimes, while the shortest(and all other) duration packet lifetime utilized may be significantlysmaller (e.g., 20 ms) than conventional packet lifetimes. Thus, thetotal amount of time to transmit a video utilizing embodiments of thepresent invention will take less time than a conventional method ordevice.

In some embodiments of the invention, relative importance of a packetmay be based on a video frame type. For example, H.264 video encodersproduce various types of video frames, such as “I frames,” “P frames,”and “B frames,” that each carry different types of information. I framestypically carry more information than P frames, and P frames typicallycarry more information than B frames. More specifically, I frames areindependent frames that generally contain the full informationassociated with an individual image frame. P frames are dependent on oneor more previous (e.g., I) frames, generally defining a difference ordelta in the associated image relative to the previous frames, which mayresult in greater compression than I-frames. B frames are dependent onone or more previous or forward frames and generally result in thehighest amount of data compression.

In some embodiments of the invention, packets containing I frame datamay be assigned a greater importance or priority value than packetscontaining P frame data, which may be assigned a greater importancevalue or priority than packets containing B frame data. I frames may beassigned a greater importance than P or B frames because a loss of an Iframe may more significant degrade video quality than a loss of a Pframe or a B frame, for example, because other video frames are notrequired to decode I frames (i.e., I frames carry full information anddo not use information from other frames). In other words, I frames aremore important than P frames and B frames because I frames are viewableby themselves. P frames may be assigned a greater importance than Bframes because, in a lossy network, there is a twice as high a chancethat a P frame will be decoded than a B frame because it is twice aslikely that either one of the previous or forward frames of a B framewhich are both necessary for decompressing the B frame could be lost,than the chance of losing only a previous frame used to decompress the Pframe. As packets are assigned retry limits and packet lifetimesproportionally to their importance, I frame packets may be assignedgreater retry limits and packet lifetimes than P frame packets, which inturn may be assigned greater retry limits and packet lifetimes than Bframe packets. According to such embodiments fewer I frame packets(relative to P frame packets) and fewer P frame packets (relative to Bframe packets) may be dropped, as compared to conventional systems whichset the same retry limits and packet lifetimes for all I, P and B framesand thus drop all I, P and B frames with the same probability.

Thus, by adjusting retry limit and/or packet lifetime based on the typeof video frame of the packet attempting to be transmitted, more time orattempts for transmission can be allowed for packets that have a higherchance of being decoded (i.e., require fewer other packets to decode thepacket attempting to be transmitted) which results in smoother videoplayback and dropping of less frames. Similarly, by adjusting retrylimit and/or packet lifetime so that less time or attempts fortransmission are allowed for packets that have a lower chance of beingdecoded (i.e., require more other packets to decode the packetattempting to be transmitted), the speed by which a device can transmita video can be increased by reducing congestion.

Additionally or alternatively, the relative importance of the packet maybe proportional to an order or number of a fragment of a frame. Asubsequent (Nth) fragment of a frame may be assigned a higher importancevalue, and thus a proportionally higher retry limit and/or packetlifetime, as compared to a prior (N−1th) fragment of the frame. Thelater the subsequent fragment is transmitted, the more prior fragmentshave already been transmitted successfully, and thus the more there isto lose by the loss of a subsequent fragment. In contrast, for a firstor prior fragment, there is no or less cost incurred for the frame sofar, and its loss would result in less cumulative data lost. In variousembodiments, there may be N relative importance values for each Nfragments, M relative importance values for different groups offragments, e.g., two relative importance values (a lower value for thefirst fragment and a higher value for the second or greaterfragment(s)).

Additionally or alternatively, relative importance of a packet may beinversely proportional to a success streak value (or inverselyproportional to a failure streak value) of the success (or failure) oftransmitting a sequence of packets associated with one or more videoframes. For example, if the streak value is greater than a predeterminedpositive threshold value, then the transmission of video frames has beenrelatively successful and a loss of a packet would be minimally harmful;whereas if the streak value is less than the predetermined value, thenone or more recent frame transmissions have failed and therefore thecurrent video frame transmission is given a higher importance value tocompensate for the poor performance to maintain a predefined level ofvideo quality.

For example, a streak counter can be initialized to zero. Each time apacket is successfully transmitted, the streak counter may be increasedby one. Each time a packet is dropped, the streak counter may bedecreased by 1. In some embodiments of the invention, a streak counteris maintained for each type of video frame (e.g., I, P, and B frames). Astreak value for I frames may be continuously updated for every I frame(without resetting in between) because the I frames carry fullinformation and do not use information from other frames. The streakvalue for P and B frames may be reset for every new I frame or Group ofPictures (“GOP”) and updated thereafter because the P and B framescontain incremental information on top of the I frame which istransmitted at the beginning of every GOP. P and B frame streak countersmay be reset each GOP because success/failure streaks from previous GOPsare of no significance to a current GOP as P and B frames only need touse adjacent packets for decoding.

In some embodiments of the invention, relative importance of the packetmay be based on any combination of a video frame type, an order of aframe fragment, and a success/failure streak of packets for a videoframe. The importance of a packet may be computed, for example, as aweighted sum of a combination of two or more of these factors. In oneexample, the video frame type factor may have a greater weight than theorder of frame fragment factor, which in turn may have a greater weightthan the success/failure streak factor, although other weights,hierarchies or orders of factor importance may be used.

Regarding the type of video frame a packet belongs to: I frames may beassigned the highest importance because I frames contain fullinformation or picture (e.g., I frames do not require other video framesto decode), and losing I frames has a greater effect on video qualitythan losing P or B frames. P frames and B frames may be assigned lessimportance than I frames because P frames and B frames containincremental information with respect to I and previous and future P andB frames. P frames may be assigned a higher importance than B framesbecause P frames are less reliant on the successful transmission ofother frames than B frames because P frames use data from previousframes for decoding, whereas B frames use data from both previous andsubsequent frames to decode.

Regarding an amount of a frame already transmitted, subsequent fragmentsof a frame (2^(nd) onwards) may be given a higher weight compared toprior fragment of the frame during transmission, for example, because ifone or more fragments of a frame are already transmitted successfully,then a part of the video frame is already at the receiver and, thus, itis important to transmit the remaining fragments (and portion) of thevideo frame so the receiver can reassemble the frame from the fragments,decode and play it. In contrast, before attempting to transmit a firstfragment of a video frame, no other fragments of that video frame havebeen already transmitted, such that, if there is an indication ofcongestion, the whole frame could be discarded if the first fragmenttransmission fails.

Regarding success/failing streak, if the streak value is greater than acertain positive value, then the transmission of video frames belongingto that video frame type have been successful, and, therefore, thecurrent video frame transmission may assume normal or reduced priority.If the streak value is smaller than a predetermined value, then recentframe transmissions have failed, and, therefore, the current video frametransmission may be given higher priority to maintain video quality.

The MAC layer may use the importance index to get the values for packetlifetime, retry limit, and any other parameters to be used fortransmitting the packet. In some embodiments of the invention, the MAClayer may use an importance index table, for example, as follows:

Video Frame First/Subsequent Packet Importance Type fragment Streakvalue Index I Subsequent <=5 0 I Subsequent >5 1 I First <=5 2 IFirst >5 3 P Subsequent <=2 4 P Subsequent >2 5 P First <=2 6 P First >27 B Subsequent <=4 8 B Subsequent >4 9 B First <=4 10 B First >4 11

Packet Importance Index 0 may correspond to the highest importance,whereas Packet Importance Index 11 may correspond to the lowestimportance.

Apart from video frame type, an order of a frame fragment, and asuccess/failure streak of packets for a video frame, any otherimportance information generated by an encoding layer could be used incombination with the above parameters to determine the relativeimportance of video packets.

In some embodiments of the invention, when the MAC layer takes up avideo packet (fragment of a video frame) for transmission, the MAC layercan determine the importance index for the packet using the anycombination of video frame type to which the packet belongs, whether itis the first fragment or the subsequent fragment of the frame; and thestreak counter value for the video frame type. The MAC layer maydetermine the packet lifetime and retry limit using the importance indexand configures and starts packet transmission.

Values chosen for packet lifetime and retry limits may also depend onthe application. Packet lifetime values may depend on the playout delayand/or buffering that the video application can afford. For interactiveapplications like video conferencing, which cannot afford large delaysand buffering, the packet lifetime value cannot be too large. In otherwords, packet lifetime value may be smaller for interactive applicationsthan for applications that can handle larger delays and buffering, suchas, non-interactive applications, like video streaming. For applicationswhich cannot afford large delays and buffering, the maximum packetlifetime corresponding to a highest importance may not be bigger thane.g., approximately 200 ms. Otherwise, the delays and/or buffering maybe visible to human eyes. Whereas for non-interactive applications, likevideo streaming, which can afford larger delays and buffering, themaximum packet lifetime value corresponding to a highest importance canbe e.g., in a range of from approximately 200 ms to 500 ms. Packetlifetimes for other importance values may be derived from the maximumvalue linearly down to a minimum value of 20 ms, for example, such thatone 1500 byte packet takes approximately 12 ms at 1 Mbps to allow atleast one transmission attempt at the lowest possible WLAN rate.

Retry limit values may depend on power consumption and may also be usedto limit the number of transmissions in the network to avoid networkcongestion. Retry limit values may be kept low for packets of lowimportance and high for packets of high importance becauseretransmissions affect network congestion negatively when there are manydevices in the network, which in turn affects overall networkperformance. Transmissions also affect power consumption and, therefore,for battery powered devices, it is important to reduce transmissions.Thus, selecting retry limits based on packet importance may help reducepower consumption and overall network efficiency.

In some embodiments of the invention, the retry limit value for packetswith the highest importance may be set e.g., to 24 retry attempts,before terminating, and the retry limit values for packets with lowerimportance may be derived from this maximum value linearly down to aminimum of e.g., 2 retry attempts, for lowest importance, as can be seenin the example table below.

Importance index Packet lifetime Packet retry limit 0 200 ms  24 1 150ms  16 2 100 ms  14 3 80 ms 12 4 80 ms 10 5 70 ms 8 6 60 ms 6 7 50 ms 48 50 ms 4 9 40 ms 2 10 30 ms 2 11 20 ms 2

When a packet exceeds either the packet lifetime or the retry limit,that packet may be discarded and, in some embodiments, the streakcounter may be restarted.

In some embodiments of the invention, a default or minimum packetlifetime and/or retry limit value, such as e.g., 20 ms and/or 2 tries,may be utilized at the beginning of every packet transmissionirrespective of the packet's importance, and may be increased forpackets with relatively high or above threshold importance or priorityvalues.

Multiple different tables mapping the importance index to packettransmission parameters, such as packet lifetime and retry limit, may bemaintained and used. One of the tables could be used at any point intime based on certain criteria, such as MAC transmit rate and/or videopacket queue backlog. The MAC transmit rate is the rate selected by theMAC layer, based on transmit statistics, for the transmission ofpackets. IEEE 802.11 bgn 1×1 supports 20 transmit rates ranging from 1mbps to 65 mbps as shown below:

Rate in mbps 1 2 5.5 6 6.5 9 11 12 13 18 19.5 24 26 36 39 48 52 54 58.565

The current transmit rate reflects the throughput being achieved by thedevice affected by range, interference and congestion. The higher thetransmit rate is, the higher the throughput is, and vice versa. Queuebacklog directly reflects the throughput being achieved by the device inprevailing conditions. If the queue backlog is high, it indicates thethroughput is low and packets may start getting dropped due to lack ofmemory for new packets sent by higher layers to MAC. In such conditions,instead of dropping packets at the source, it is advantageous to speedup transmission and recycling of packets at the other end.

An example of multiple different tables mapping the importance index topacket transmission parameters is shown for example as follows:

Table 1 Table 2 Table 3 Packet Packet Packet Packet Packet PacketImportance lifetime retry lifetime retry lifetime retry index (ms) limit(ms) limit (ms) limit 0 200 24 100 12 50 6 1 150 16 75 8 37 4 2 100 1450 7 25 3 3 80 12 40 6 20 3 4 80 10 40 5 20 2 5 70 8 35 4 17 2 6 60 6 303 15 1 7 50 4 25 2 12 1 8 50 4 25 2 12 1 9 40 2 20 1 10 0 10 30 2 15 1 70 11 20 2 10 1 5 0

In some embodiments of the invention, a frame may be dropped without anyattempt to transmit, if the lifetime is less than the packet duration orretry limit is zero.

Reference is made to FIG. 1A which schematically illustrates a systemfor wirelessly transmitting a sequence of video packets over a wirelesslocal area network (“WLAN”) with a device, in an Access Point (“AP”)mode, according to an embodiment of the invention.

The system of FIG. 1A may include a transmitting device 101 which cantransmit video packets 109 over a WLAN to a receiving device 105. Thetransmitting device 101 can be a video camera with a WLAN interface, asmartphone, a personal computer, desktop computer, mobile computer,laptop computer, and notebook computer, or any other suitable devicesuch as a personal digital assistant (PDA), video game console, etc.

The transmitting device 101 can include an antenna or transceiver 103for transmitting the video packets 109 to the receiving device 105. Thetransmitting device 101 can include a processor 113 which can executesoftware residing in an operating system (“OS”) 115. The transmittingdevice 101 can include a memory 111. The memory 130 can include, forexample, a read only memory (“ROM”), a random access memory (“RAM”), adynamic RAM (“DRAM”), a flash memory, a volatile memory, a non-volatilememory, a cache memory, a buffer, or other suitable permanent, long-termor short-term memory units or storage units. The transmitting device 101can include a camera 116 or be in communication with an external camera.

In some embodiments of the invention, the processor 113 may beconfigured to compute an importance metric associated with a priority oftransmitting each individual packet of the one or more video framestransmitted by the transmitting device 101. The processor 113 may beconfigured to determine a retry limit and/or packet lifetime for eachindividual video packet in the sequence of video packets 109 based onthe importance metric associated with the priority of transmitting theindividual video packet 109. The processor 113 may be configured toattempt to transmit each video packet in the sequence of video packetsvia transceiver 103. The processor 113 may be configured to, uponreceiving a message indicating that the transmission attempt for anindividual video packet 109 in the sequence failed, repeat attempting totransmit the individual video packets 109 for up to the retry limit orpacket lifetime determined for the individual video packet 109 or untila successful transmission is achieved.

In some embodiments of the invention, the processor 113 is configured todynamically adjust the retry limit or packet lifetimes in real time. Theprocessor 113 can be configured to independently determine the retrylimit or packet lifetimes to be directly proportional to the importancemetric of each video packet 109. The processor 113 can be configured tocompute the importance metric of the video packet 109 based on one ormore of the following factors: a video frame type, an order of a framefragment, and a success or failure streak of the sequence of videopackets.

In some embodiments of the invention, the processor 113 is configured tocompute the importance metric of the video packet based on the videoframe type of the video packet 109, configured to assign a video packet109 associated with an I video frame a higher importance metric than avideo packet 109 associated with a P frame, and configured to assign avideo packet 109 associated with a P frame a higher importance metricthan a video packet associated with a B frame.

In some embodiments of the invention, the processor 113 may compute theimportance metric of the video packet 109 based on the order of theframe fragment, such that a packet 109 associated with a subsequent(Nth) frame fragment is assigned a relatively greater importance metricthan a prior (N−1th) frame fragment. The processor 113 can be configuredto maintain, in the memory 111, a separate value of the order of theframe fragment for each different video frame type. The processor 113can be configured to maintain a separate streak value, in the memory130, for each different video frame type.

In some embodiments of the invention, the processor 113 may beconfigured such that the importance metric of the video packet 109 isproportional to a streak value counting the number of successfultransmissions of a group of the video packets 109 associated with each Iframe, wherein the streak value is incremented each time one of thegroup of video packets 109 is successfully transmitted to receivingdevice 105, or decremented each time one of the group of video packets109 is not successfully transmitted to receiving device 105.

In some embodiments of the invention, the processor 113 can beconfigured to initialize an I frame streak counter at the start of a newstreaming session; initialize a P frame streak counter for each newgroup of frames associated with a new I frame; initialize a B framestreak counter for each new group of frames associated with a new Iframe; increment the I frame streak counter upon each successful I framevideo packet transmission; increment the P frame streak counter uponeach successful P frame video packet transmission; and increment the Bframe streak counter upon each successful B frame video packettransmission.

The receiving device 105 can be a smartphone, a personal computer,desktop computer, mobile computer, laptop computer, and notebookcomputer, or any other suitable device such as a personal digitalassistant (PDA), video game console, etc.) The receiving device 105 mayinclude an antenna or transceiver 107 for receiving the video packets109 transmitted by the transmitting device 101. The receiving device 105may include or be in communication with a display 117 for viewing thevideo once the necessary video packets 109 have been received by thereceiving device 105.

Reference is made to FIG. 1B which schematically illustrates a systemfor wirelessly transmitting a sequence of video packets over a wirelesslocal area network (“WLAN”) with a video camera device, in a Station(“STA”) mode, according to an embodiment of the invention.

The system of FIG. 1B may include the transmitting device 101 which cantransmit video packets 109 over a WLAN to a WLAN Access Point 119 whichin turn can transmit the video packets 109 over the WLAN to thereceiving device 105. The WLAN Access Point 119 may include an antennaor transceiver 121 for receiving the video packets 109 transmitted bytransmitting device 101, and for transmitting the video packets 109 tothe receiving device 105.

Reference is made to FIG. 2 which schematically illustrates a videostreaming system 200, according to an embodiment of the invention.

The video streaming system 200 can include a video camera 201 (e.g.,camera 116 of FIGS. 1A and 1B), a video encoder 203, and a WLANSystem-on-a-chip (“WLAN SoC”) device 205 (e.g., processor 113 of FIGS.1A and 1B). The video encoder 203 can be configured to encode image(s),audio, and/or videos captured by video camera 201, and transmit theencoded data to the WLAN SoC 205.

The WLAN SoC 205 can include a video application 207, a Real-timeTransport Protocol/User Datagram Protocol Network (“RTP/UDP NW”) 209,WLAN MAC layer protocol 211, and a WLAN Physical Layer or medium (“WLANPHY”) 213.

The RTP/UDP 209 may be a network protocol for delivering audio and videoover the network. The format of the MAC frames can be specified in theWLAN MAC layer protocol. The WLAN PHY 213 can interface a physicalmedium with the MAC and upper layers.

Reference is made to FIG. 3 which schematically illustrates a WLAN MACsubsystem 300, according to an embodiment of the invention.

The WLAN MAC subsystem 300 (e.g., the WLAN MAC 211 of FIG. 2) caninclude video packets 301 (e.g., video packets 109 of FIGS. 1A and 1B),a MAC transmit queue 303, a MAC Channel Access Function 305, a MACTransmit Function 307, and a MAC Lifetime Timer 309.

The MAC Channel Access Function 304 can be configured to connect to achannel, and, upon successful channel acquisition, the MAC TransmitFunction 307 is configured to transmit the packet 301. If the packettransmission is successful, the WLAN MAC subsystem 300 is configured tomove on to a next packet. The MAC Transmit Function 307 can beconfigured to, if transmission of the packet 301 fails, e.g., asinferred by a missing acknowledgement from a receiver (e.g., thereceiving device 105 of FIGS. 1A and 1B), retransmit the packet 301. TheMAC Transmit Function 307 can be configured to continue to retransmitthe failed packet 301 until the MAC Lifetime Timer 309 detects that theretry limit is reached or the packet 301 exceeds its lifetime, whicheveroccurs first. If the retry limit is reached or the packet 301 exceedsits lifetime, the packet is dropped and no further attempt is made totransmit the packet.

Reference is made to FIG. 4 which illustrates an example of a frame typebreakdown of two groups of pictures (“GOP”), according to an embodimentof the invention.

The first GOP 401 may start with an I frame 405 followed by a pluralityof B frames 409 and P frames 413. The second GOP 403 may start with an Iframe 407 followed by a plurality of B frames 411 and P frames 415.

Reference is made to FIG. 5 which illustrates a flowchart of a method500 for wirelessly transmitting a sequence of video packets containingvideo data for one or more video frames, according to an embodiment ofthe invention.

In operation 501, a processor (e.g., processor 113 of FIGS. 1A and 1B)may independently compute an importance metric associated with apriority of transmitting each individual packet in the sequence of videopackets.

In operation 503, the processor may independently determine a retrylimit or packet lifetime for each individual video packet in thesequence of video packets based on the importance metric associated withthe priority of transmitting the individual video packet, such that atleast a plurality of packets have different retry limits or packetlifetimes. In some embodiments of the invention, the processor isconfigured to dynamically adjust the retry limit or packet lifetimes inreal time. The processor may determine the retry limit or packetlifetime such that the retry limit or packet lifetime is directlyproportional to the importance metric of each video packet.

In some embodiments of the invention, the processor may compute theimportance metric of the video packet based on the video frame type ofthe video packet, and a video packet associated with an I video framehas a higher importance metric than a video packet associated with a Pframe, which in turn has a higher importance metric than a video packetassociated with a B frames.

In some embodiments of the invention, the processor may compute theimportance metric of the video packet based on the order of the framefragment, such that a packet associated with a subsequent (Nth) framefragment is assigned a relatively greater importance metric than a prior(N−1th) frame fragment. The processor may maintain a separate value ofthe order of the frame fragment in a memory (e.g., memory 111 of FIGS.1A and 1B) for each different video frame type.

In some embodiments of the invention, the importance metric of the videopacket may be computed based on a streak value that is proportional tothe number of successful transmissions of a group of the video packetsassociated with each I frame, wherein the streak value is incrementedeach time one of the group of video packets is successfully transmitted,and/or decremented each time one of the group of video packets is notsuccessfully transmitted. The processor may maintain a separate streakvalue in the memory for each different video frame type, or a combinedstreak value for all frame types.

In some embodiments of the invention, the processor may initialize an Iframe streak counter at the start of a new streaming session; initializea P frame streak counter for each new group of frames associated with anew I frame; initialize a B frame streak counter for each new group offrames associated with a new I frame; increment the I frame streakcounter upon each successful I frame video packet transmission;increment the P frame streak counter upon each successful P frame videopacket transmission; and increment the B frame streak counter upon eachsuccessful B frame video packet transmission.

In operation 505, the processor may attempt to transmit each videopacket in the sequence of video packets, via a transceiver (e.g., thetransceiver 103 of FIGS. 1A and 1B).

If the transmission is successful, the transmission process for thevideo packet stops at operation 507. However, if the processor receivesa message indicating that the transmission attempt for the video packetin the sequence failed, or does not receive a message indicating thatthe transmission attempt for the video packet has succeeded, inoperation 509, the processor may repeat attempting to transmit theindividual video packet for up to the number of tries or packet lifetimeindependently determined for the individual packet or until a successfultransmission is achieved.

Reference is made to FIG. 6 which is a flowchart of a method forselecting one of a plurality of parameter tables based on a transmissionrate, according to an embodiment of the invention.

The method begins in operation 601. In operation 603, a processor (e.g.,the processor 113 from FIGS. 1A and 1B) determines if the transmissionrate is greater than a first predetermined threshold, e.g., 24 mb/s. Ifthe transmission rate is greater than the first predetermined thresholdin operation 603, then, in operation 605, the processor uses Table 1,shown below, to determine the packet lifetimes and retry limits:

Table 1 Table 2 Table 3 Packet Packet Packet Packet Packet PacketImportance lifetime retry lifetime retry lifetime retry index (ms) limit(ms) limit (ms) limit 0 200 24 100 12 50 6 1 150 16 75 8 37 4 2 100 1450 7 25 3 3 80 12 40 6 20 3 4 80 10 40 5 20 2 5 70 8 35 4 17 2 6 60 6 303 15 1 7 50 4 25 2 12 1 8 50 4 25 2 12 1 9 40 2 20 1 10 0 10 30 2 15 1 70 11 20 2 10 1 5 0

If, in operation 603, the processor determines that the transmissionrate is not greater than the first predetermined threshold, then, inoperation 607 the processor determines if the transmission rate isgreater than a second predetermined threshold, e.g., 11 mb/s. If thetransmission rate is greater than the second predetermined threshold,then, in operation 609, the processor uses the above Table 2 todetermine the packet lifetimes and retry limits. If, in operation 607,the processor determines that the transmission rate is not greater thanthe second predetermined threshold, then, in operation 611, theprocessor uses the above Table 3 to determine the packet lifetimes andretry limits. This process may continue for any number of Npredetermined thresholds and associated tables.

In some embodiments, the multiple tables are provided to set the packetlifetimes and retry limits to values scaled or proportional to thetransmission rates of the system. Lower transmission rates may use morechannel time to complete a transmission than higher transmission rates;however, lower transmission rates are typically more reliable (e.g., mayrequire less retries) than higher transmission rates to complete thetransmission). As explained above, the higher the transmit rate is, thehigher the throughput is, and vice versa. When the transmissionrate/throughput is low, in such conditions, instead of dropping packetsat the source, it is advantageous to speed up transmission and recyclingof packets at the other end. Thus, in some embodiments of the invention,a table for a lower transmission rate may have smaller packet lifetimesand/or packet retry limits for each importance index than a table for alarger transmission rate.

Reference is made to FIG. 7 which is a flowchart of a method forselecting one of a plurality of parameter tables based on a queuebacklog, according to an embodiment of the invention

The method begins in operation 701. In operation 703, a processor (e.g.,the processor 113 from FIGS. 1A and 1B) determines if the queue backlogis less than a first predetermined number, e.g., 20. If the queuebacklog is less than the first predetermined number in operation 703,then, in operation 705, the processor uses Table 1, shown below, todetermine the packet lifetimes and retry limits:

Table 1 Table 2 Table 3 Packet Packet Packet Packet Packet PacketImportance lifetime retry lifetime retry lifetime retry index (ms) limit(ms) limit (ms) limit 0 200 24 100 12 50 6 1 150 16 75 8 37 4 2 100 1450 7 25 3 3 80 12 40 6 20 3 4 80 10 40 5 20 2 5 70 8 35 4 17 2 6 60 6 303 15 1 7 50 4 25 2 12 1 8 50 4 25 2 12 1 9 40 2 20 1 10 0 10 30 2 15 1 70 11 20 2 10 1 5 0

If, in operation 703, the processor determines that the queue backlog isnot less than the first predetermined number, then, in operation 707 theprocessor determines if the queue backlog is less than a secondpredetermined number. If the queue backlog is less than the secondpredetermined number, then, in operation 709, the processor uses theabove Table 2 to determine the packet lifetimes and retry limits. If, inoperation 707, the processor determines that the queue is not less thanthe second predetermined number, then, in operation 711, the processoruses the above Table 3 to determine the packet lifetimes and retrylimits.

In some embodiments, the multiple tables are provided in FIG. 7 to setthe packet lifetimes and retry limit to values scaled or inverselyproportional to the transmission queue backlog of the system. Asexplained above, a relatively high queue backlog may indicate that thethroughput is relatively low and packets may start getting dropped dueto lack of memory for new packets sent by higher layers to MAC. In suchconditions, instead of dropping packets at the source, it isadvantageous to speed up transmission and recycling of packets at theother end. Thus, in some embodiments of the invention, a table for alarger queue backlog may have smaller packet lifetimes and/or packetretry limits for each importance index than a table for a smaller queuebacklog.

Example Analysis of Video Performance Improvement

An example video encoder (e.g., 203 of FIG. 2) may generate a 1 mbpsvideo stream. An RTP layer may packetize the video stream into 1400 bytevideo packets. The packet rate is therefore approximately 90 packets/secinput into the MAC layer for transmission, which is approximately onepacket every 11 ms. The following packet sequence may be used composedof 14 packets belonging to one GOP and corresponding importance indexderived based on above scheme.

Example

Because I frames are typically larger (contain more information) than Bframes and P frame, the above example depicts an example of a single Iframe broken down into 3 packets I1, I2, and I3 to meet Real-timeTransport Protocol (“RTP”) packet size requirements. Because P and Bframes are typically smaller than I frames, P and/or B frames may befragmented into one or more than one packet (depending on the frame andpacket sizes) to meet RTP packet size requirements.

The following tables show the packet lifetime and retry limits appliedfor this sequence of packets with various transmit parameter tables.Table A is generated without applying the above scheme, and Tables B-Ddefine packet lifetime and retry limit data for the above Table 1, Table2, and Table 3, respectively.

TABLE A without applying the above scheme Importance Packet Index PacketLifetime Retry Limit I1 0 200 8 I2 0 200 8 I3 0 200 8 B 0 200 8 B 0 2008 B 0 200 8 P 0 200 8 B 0 200 8 B 0 200 8 B 0 200 8 P 0 200 8 B 0 200 8B 0 200 8 B 0 200 8 Aggregate 2,800 112

TABLE B based on Table 1 Importance Packet Index Packet Lifetime RetryLimit I1 2 100 14 I2 0 200 24 I3 0 200 24 B 10 30 2 B 10 30 2 B 10 30 2P 6 60 6 B 10 30 2 B 10 30 2 B 11 20 2 P 6 60 6 B 11 20 2 B 11 20 2 B 1120 2 Aggregate 0 850 92

TABLE C based on Table 2 Importance Packet Index Packet Lifetime RetryLimit I1 2 50 7 I2 0 100 12 I3 0 100 12 B 10 15 1 B 10 15 1 B 10 15 1 P6 30 3 B 10 15 1 B 10 15 1 B 11 10 1 P 6 30 3 B 11 10 1 B 11 10 1 B 1110 1 Aggregate 0 425 46

TABLE D based Table 3 Importance Packet Index Packet Lifetime RetryLimit I1 2 25 3 I2 0 50 6 I3 0 50 6 B 10 7 0 B 10 7 0 B 10 7 0 P 6 15 1B 10 7 0 B 10 7 0 B 11 5 0 P 6 15 1 B 11 5 0 B 11 5 0 B 11 5 0 Aggregate0 210 17

In a “worst-case” scenario, conventional fixed values for packetlifetime and retry limit may be, for example, 2800 ms and 112. Althoughthis worst-case may not be hit, packet lifetime and retry limit couldstill be high in the presence of poor transmission performance,resulting in high delay and packet loss, irrespective of importance ofpacket. Whereas, according to embodiments of the invention, packetlifetime and retry limit are configured dynamically to adjust tooperating conditions and avoid delay and loss for important packets.

In the foregoing description, various aspects of the present inventionare described. For purposes of explanation, specific configurations anddetails are set forth in order to provide a thorough understanding ofthe present invention. However, it will be apparent to one of ordinaryskill in the art that embodiments of the present invention may bepracticed without the specific details presented herein. Furthermore,well known features may be omitted or simplified in order not to obscurethe present invention.

Although embodiments of the invention are not limited in this regard,discussions utilizing terms such as, for example, “processing,”“computing,” “calculating,” “determining,” “establishing”, “analyzing”,“checking”, or the like, may refer to operation(s) and/or process(es) ofa computer, a computing platform, a computing system, or otherelectronic computing device, that manipulates and/or transforms datarepresented as physical (e.g., electronic) quantities within thecomputer's registers and/or memories into other data similarlyrepresented as physical quantities within the computer's registersand/or memories or other information non-transitory storage medium thatmay store instructions to perform operations and/or processes. Althoughembodiments of the invention are not limited in this regard, the terms“plurality” and “a plurality” as used herein may include, for example,“multiple” or “two or more”. The terms “plurality” or “a plurality” maybe used throughout the specification to describe two or more components,devices, elements, units, parameters, or the like. The term set whenused herein may include one or more items. Unless explicitly stated, themethod embodiments described herein are not constrained to a particularorder or sequence. Additionally, some of the described methodembodiments or elements thereof can occur or be performedsimultaneously, at the same point in time, or concurrently.

The invention claimed is:
 1. A method of wirelessly transmitting asequence of video packets containing video data for one or more videoframes, the method comprising: independently computing an importancemetric associated with a priority of transmitting each individual packetin the sequence of video packets; independently determining a packetlifetime for each individual video packet in the sequence of videopackets based on the importance metric associated with the priority oftransmitting the individual video packet, wherein the packet lifetime isa maximum duration of time allowed for multiple repeat transmissions ofthe individual video packet; attempting to transmit each video packet inthe sequence of video packets; and upon receiving a message indicatingthat the transmission attempt for an individual video packet in thesequence failed, repeating attempting to transmit the individual videopackets: for up to the packet lifetime independently determined for theindividual packet, or until a successful transmission is achieved beforethe packet lifetime has been reached.
 2. The method of claim 1, whereinthe packet lifetime of the video packets is dynamically adjusted inreal-time.
 3. The method of claim 1, wherein the packet lifetime of thevideo packets are independently determined to be directly proportionalto the importance metric of each video packet.
 4. The method of claim 1,wherein the importance metric of the video packet is computed based onone or more factors selected from the group consisting of: a video frametype, an order of a frame fragment, and a success or failure streak ofthe sequence of video packets.
 5. The method of claim 4, wherein theimportance metric of the video packet is computed based on the videoframe type of the video packet, and a video packet associated with an Ivideo frame has a higher importance metric than a video packetassociated with a P frame, which in turn has a higher importance metricthan a video packet associated with a B frames.
 6. The method of claim4, wherein the importance metric of the video packet is computed basedon the order of the frame fragment, such that a packet associated with asubsequent (Nth) frame fragment is assigned a relatively greaterimportance metric than a prior (N−1th) frame fragment.
 7. The method ofclaim 6 comprising maintaining a separate value of the order of theframe fragment for each different video frame type.
 8. The method ofclaim 4, wherein the importance metric of the video packet isproportional to a streak value counting the number of successfultransmissions of a group of the video packets associated with each Iframe, wherein the streak value is incremented each time one of thegroup of video packets is successfully transmitted, or decremented eachtime one of the group of video packets is not successfully transmitted.9. The method of claim 8 comprising maintaining a separate streak valuefor each different video frame type.
 10. The method of claim 9,comprising: initializing an I frame streak counter at a start of a newstreaming session; initializing a P frame streak counter for each newgroup of frames associated with a new I frame; initializing a B framestreak counter for each new group of frames associated with the new Iframe; incrementing the I frame streak counter upon each successful Iframe video packet transmission; incrementing the P frame streak counterupon each successful P frame video packet transmission; and incrementingthe B frame streak counter upon each successful B frame video packettransmission.
 11. The device of claim 8, wherein the processor isconfigured to maintain a separate streak value for each different videoframe type.
 12. The device of claim 11, wherein the processor isconfigured to: initialize an I frame streak counter at a start of a newstreaming session; initialize a P frame streak counter for each newgroup of frames associated with a new I frame; initialize a B framestreak counter for each new group of frames associated with the new Iframe; increment the I frame streak counter upon each successful I framevideo packet transmission; increment the P frame streak counter uponeach successful P frame video packet transmission; and increment the Bframe streak counter upon each successful B frame video packettransmission.
 13. The method of claim 1, wherein the packet lifetimesare independently determined to be proportional to the importance metricfor each video packet.
 14. A device for wirelessly transmitting asequence of video packets containing video data for one or more videoframes, the device comprising: a processor configured to: independentlycompute an importance metric associated with a priority of transmittingeach individual packet in the sequence of video packets, independentlydetermine a packet lifetime for each individual video packet in thesequence of video packets based on the importance metric associated withthe priority of transmitting the individual video packet, wherein thepacket lifetime is a maximum duration of time allowed for multiplerepeat transmissions of the individual video packet, attempt to transmiteach video packet in the sequence of video packets, and upon receiving amessage indicating that the transmission attempt for an individual videopacket in the sequence failed, repeat attempting to transmit theindividual video packets: for up to the packet lifetime independentlydetermined for the individual packet, or until a successful transmissionis achieved before the packet lifetime has been reached.
 15. The deviceof claim 14, wherein the processor is configured to dynamically adjustthe packet lifetime of the video packets in real-time.
 16. The device ofclaim 14, wherein the processor is configured to determine the packetlifetime of the video packets to be directly proportional to theimportance metric of each video packet.
 17. The device of claim 14,wherein the processor is configured to compute the importance metric ofthe video packet based on one or more factors selected from the groupconsisting of: a video frame type, an order of a frame fragment, and asuccess or failure streak of the sequence of video packets.
 18. Thedevice of claim 17, wherein the processor is configured to compute theimportance metric of the video packet based on the video frame type ofthe video packet, and a video packet associated with an I video framehas a higher importance metric than a video packet associated with a Pframe, which in turn has a higher importance metric than a video packetassociated with a B frames.
 19. The device of claim 17, wherein theprocessor is configured to compute the importance metric of the videopacket based on the order of the frame fragment, such that a packetassociated with a subsequent (Nth) frame fragment is assigned arelatively greater importance metric than a prior (N−1th) framefragment.
 20. The device of claim 19, comprising a memory, wherein theprocessor is configured to maintain a separate value of the order of theframe fragment for each different video frame type in the memory. 21.The device of claim 17, comprising a memory, wherein the processor isconfigured to: determine the importance metric of the video packet to beproportional to a streak value counting the number of successfultransmissions of a group of the video packets associated with each Iframe; store the streak value in the memory, and increment the streakvalue each time one of the group of video packets is successfullytransmitted, or decremented each time one of the group of video packetsis not successfully transmitted.